Burner for heavy fuels



United States Patent BURNER FOR HEAVY FUELS Ward J. Bloomer, Westfield,N. J., assignor to The Lummus Company, New York, N. Y., a corporation ofDelaware Application December 24, 1952, Serial No. 327,892

4 Claims. (Cl. 158-4) Thisvinvention is an improvement on my priorinventions relating to fixed centrifugal or vortical fuel burning asgenerally set forth in applications for Patent Serial No. 66,445, filedDecember 2l, 1948 and Serial No. 98,976, filed lune 14, 1949, nowPatents Number 2,560,074 and 2,560,076.

The present application is a continuation-in-part of my applicationSerial No. 151,023, filed March 2l, 1950, now abandoned.

ln the aforesaid cases I have disclosed an improved type of burner forvarious fuels such as oil, gas and pulverized solids, such as coal. Ingeneral, a vortex of air is established within an open-ended, annular orcylindrical tuyre by forcing the air at a relatively high velocitybetween the substantially tangentially disposed .blades forming thetuyre wall. The fuel is introduced into this vortical column in eitherof two satisfactory ways. In one form the fuel is maintained in areservoir surround ing the side wall of the tuyre adjacent the closedend and the incoming air passing over the fuel, entrains the fuel andcarries itvinto the tuyre. Alternatively, a fuel distributing means isprovided which extends through the closed end of the tuyre, and beingspaced from the central axis, the fuel is introduced directly into thevortical column. This assures uniform distribution and avoids theresistance to the introduction of the fuel, by the rapidly rotatinginner wall of the column. `The atomization of the fuel and thoroughdispersion into the column is completed in the tuyre and the combustiblemixture is then discharged into a combustion chamber or throat spacedfrom the tuyre. throat serves as a radiant chamber to maintainuniformity of combustion, and the tuyre due to its spaced position andthe flow of air through it, is maintained at a relatively cooltemperature.

My present invention relates more particularly to an improvedconstruction of burners which has a greater range of operation withrespect to fuels in that it is particularly adapted to burn not only thegaseous and distillate fuels but also the heavy residual fuels whichhave a higher carbon ratio than distillate fuels. The burner isparticularly effective in burning materials such as asphaltic residues.Asphalts, particularly from- Venezuela deposits are not only difficultto burn but they have a further complication in that the ash isapproximately 50% vanadium pentoxide (V205). The ash skeleton from adroplet generally forms a liyash which is not` only externally wet andsticks to the boiler and superheater tubes but also attacks the brickwork forming eutectic mixtures which tend to melt down the brick.Furthermore, the sticky vanadium slag grows in thickness until heatstresses crack the coating from its bond to the tubes forming flakes andclots which heat and soften and slide around the tube surface. Theseform obstacles in the gas stream and eventually a hard and clinker likemass throughout the tube bank forces a shut down for cleaning orretubing. It is recognized that slag deposit is caused primarily byparticles of unburn'ed or incompletely The combustion chamber orPatented J une 21, 1955 burned atomized oil and particles of unburnedunatomized oil. Y

My burner is particularly-satisfactory for combustion of such asphalticresidues which exist in very large quantities in parts of the UnitedStates and particularly in the northern part of South America. By theproper introduction of the melted asphalt into the vortical columnwithin the tuyre, I am able to obtain n an atomization such that the oildroplets are burned as a vapor so completely in the refractory throat ofthe burner that the particles of flyash have a size of the second orderof magnitude i. e. infinite ratio of surface to mass, zero inertia andgas-*like properties. They are completely Aairborne and are not thrownout in any deflected gas' stream. With their infinite surfacennass ratiothe iiyash particles radiate extremely readily to tube surface and dropin temperature so fast, as to be very much colder than the gas carryingthem. As operated in my burner the flyash, if any, has a micron sizeof100 microns or smaller ,and it does not build up slag deposits.Furthermore, there is no flame impingement on the brick Work or tubesurfaces, as there is no flame issuing from the burner throat, theintimate degree of atomization afforded by the vortex of the burner Yattached drawings in which:

Fig. l is a substantially vertical central section through a portion ofa furnace showing the generalarrangement and location 0f the burner.

Fig. 2 is a diagram-matic central vertical cross section of the burner.

Fig. 3 is a front elevation of the burner shown in Fig. 2.

Fig. 4 is a partial vertical cross section of the burner with a modifiedform of tuyre skirtor baille.

As a preferred form of embodiment my burner is particularly adapted forinstallation in the refractory side wall 10 of a furnace which may be aboiler, oil heater or other heat absorbing unit. Mounted on the sidewall of such a furnace is a so-called burner plate 11, such burner platecarrying additional refractory having an opening 12 formed into theshape of a cylinder to receive the windbox or enclosure 14 and alsoother refractory formed into a cylindrical combustion chamber 15. Thewindbox extends rearwardly into an air duct generl` ally indicated at 16which is adapted to be connected to a source of air under a slightpressure, such air being preferably preheated for thecombustion ofasphalt and other very heavy fuels. The windbox 14 also extends forwardnearly into contact with the refractory 15a which forms the rear Wall ofthe `combustion chamber.

The burner assembly includes a tuyre 18 of generallycylindricalshapbeing open at one end and having a frusto-conical plate20 surrounding the orifice. The side wall of the tuyre is provided witha plurality of generally tangential shallow vanes or blades 22 extendingthroughout the entire length of the tuyre. For economy, they may bestamped out of the tuyre wall, but it will be understood that they maybe separate blades, and they may overlap, or be streamlined as desired.These blades form a plurality of elongated substantially rectangular airinlets 23 disposed between the adjacent blades 22. The rear of the tuyreis closed by an end wall 24.

The face plate 20 of the'tuyre is preferably provided with a double rowo'f small openings 20a surrounding the orifice for'the 'free passage ofair'from the windbox 14', such air passing across the .face plate inrear of the refractory 15a whereby the face plate 2li is kept cool. Thetruste-conical face plate 20 is integrally mounted vto the edge of thetuyre blades and is freely movable with the tuyre in the ,windbox llllso that the entire burner assembly as wshown in Fig'Z may be moved intoand out of lposition as desired. The windbox 14 has a shoulderllaagainst which a packing ring 25 is placed so that the truste-conicalface plate makes a substantially gas tight seal at the edge of thewindbox 14.

The tuyre lLSlrnay be provided with a dual fuel supply. V'For the feedof a heavy liquid such as asphalt, I prefer to use a fuel distributingmeans` consisting of a pluralityof tubular nozzles 3i) whichproject'through the closed end24 ofthe tuyre about 1/2 inch and areconveniently 'chamfered at a 45 angle with the vertical. In each case-the lowermost edge of the nozzle projects furthermost into the tuyrc,These nozzles are fed from a common distribution ring 32 which in turnis supplied from afuel line 34.

The six fuel feeding nozzles 3i) extending into the closed end of thetuyre 18 have their discharge openings Vspaced uniformly a substantialdistance from the closed end wall 24 and from the oppositely disposedslots 23 of the side wall, the saidopenings defining a planeperpendicular to the longitudinal axis of the `tuyre and being uniformlyspaced on a common circle.

ln vaddition. Vl prefer to usea secondary fuel feed distributing panorreservoir 46 of a cup shape closely titting the side wall of the tuyreand spaced a small distanceaway from the closed end 24 of the tuyre. Asshown in IFig. 2 the sideof the pan 46 embraces the edge of the tuyreblades in such a manner as to form a series I used siniultaneouslyoralternatively and either liquid or gaseous fuel may be ffed in eithersystem.

The operation of the burner for burning the gas ordistillate fuelincludes Iforcingtheair fromthe duct 16 into the wind'oox or enclosurei4 and thence across the blades andfinto the-combustion chamber l5.

The continuous introduction of air through the convergeht air pathsestablishes a rotating mass, the centrifugal effectof which is toestablish a relatively dense shallow layer generally indicated at Xadjacent the side wall of the tuyre, the inner wall of such layer beingsubstantially parabolic with its vertex below the closed end of thetuyre 24. This layer may be considered to be a substantially hollowrotating column which is cylindrical on the outer wall and truncatedparabolic on the inner wall or surface. The fuel is introduced to thislayer to be entraincd in the rotating air mass and is given a spiral andhelical path in the tuyre before being discharged with air as acombustible mixture into the combustion zone. Y

Normal velocities of the entering air are approximately 70 ft./sec. Thestatic head of air is thus converted to rotational energy so that insidethe tuyre the air is caused to rotate in forced vortex motion as aparabolic of revolution. Due to the high Vvelocity-of the air and therapid rotation of the mass, the column is open throughout its lengthand-has-a'substantial vacuum in the central portion forming a line offorce :into Athe end of the tuyre perpendicular tothe closed end 241Itis observed that the column actually forms a circular intercept withthe .center of the end wall as indicated at 37. 'it is important for mypurposes that'the velocity of the air be such Vasrtotmaintainthiscolumnopenrthroughout.v '-Thefuek air thus discharges as an annulussolely adjacent the side althoughthisresults' in a veryY substantialpressure drop.V

The greater the velocity, the tighter or more nearly vcylindrical is thevortex and thus the greater the fuelpath and the greater the shearingand mixing. With 70 ft./sec. which is preferably used, l estimatetheelect of the centrifugal force to be about 600 times gravity, with a6 in. diameter tuyre.

An outstanding characteristic .of this vortical atomiza- Y tion `is-thatcombustion efficiently increases with an in# crease in velocity orringrate. ,Firsthigher flame tem-k perature improves ignition and 'flamestability, and second, a` change inthe force balance increases theratioof outward centrifugal force to inwarclviscous drag force resultingin a further decrease inoilparticle'size.

It has` proved `to 'be a characteristic of ,the burner that when theair'pressure drops, the oil pressure indicatoral-l ways shows anincrease. tex draws the v,oil from thefeed nozzles 30 to thewhirlingring 57 and ywhen `the central vacuum lessons, the oil` is not pulled sostrongly. 'This has the advantage that the*k i" manifold pressurerequired for multiple burners is only that needed-for accuratethrottlingi Control may thus be readily accomplished `by conventionalpressure control instruments reset by ,thetemperature ,of a coil outlet.,Calibrated Vorifices will ofcourse b e inserted in the various feedlines to evenly proportion a similar amount of oil to each burner.

The burning zone is within the throat or combustion chamber `-1Sso`spacedfrorntheend of rthe tuyre as .to relieve the tuyrefof-thenecessity for withstanding combustion temperatures. The spacing ofthecombustion zone l5 from-the mixing zone of thevtuyre is accomplished bymaintainingthedlow of air betweenblades in opposition to the centrifugaleffect of the column whereby the fuel` air column VXmoves outwardly intothe throat or combustionchamber. By properly arranging the blade angleVand bymaintaining lthe 'desired air inlet velocity and byintroducing'thefuel adjacent theclosed end of the tuyre thereis anintimate dispersion of the 'fuel in the air. `In addition heat from thecombustion chamber tends to `'ra.

-diate into the substantially open column to produce'a `highly effectivepartially heated fuel air mixture 'by the',

time it discharges'` into the combustion chamber.

The tdistance ofthe combustion zone within the refrac-V tory :throat 15is ycontrollable Vthrough variation o'frthe t 'relative` dimensions ofthe tuyre and-throat, the lratio of tangential toY axial `velocity ofthe air-fuelmix as vit/enters the combustion chamber, the linearvelocity of this mix`` ture as it emerges from the tuyre annulus. It isalso de pendent-onthe fuel-air ratio. This ratio is afunction 'of theairpressure in the windbox 14 and of theinitial velocity of the aircolumn impressed upon the burner before the air column reaches theentrainment zone adjacent the closed end-of thetuyre It is alsodependentupon'the ratio of the ydiameter ofthe tuyre -18 to the -lengthofthe blades V22. t Bor example, doubling theV tuyre diameter andhalving the blade length, while having the same-blade area, pressuredrop and air capacity in the burner, 'pro-k Y vides four times the crosssectional area in the tuyre out-L let orifice. For this reason :thelinear velocity is reduced in square root proportion to the 'increase indiameter and vthe pattern of the combustion zone wouldthus be varied Yaccordingly b y variation of the diameter-length ratio. Or-

:dinarilyl 'find thatpa ratio ofxgreater length than diameter is themostadvantageous.foratomization due to thepro- The violencetof thecenter vor-z portionately greater energy for atomization which existswith the smaller radius.

The effect of the rapidly rotating vortex within the tuyre 18 on liquidfuel from the nozzles 30 will thus be appreciated. It has been observedthat the line of force into the closed end of the tuyre is due to anegative pressure of nearly inches of water which violently draws influe gas establishing a path partially across the bottom and thenceoutward along the definition between the vortex and the rotating air-oilenvelope. This line of force then extends out of the tuyre and rolls onitself as an inner eddy in the refractory throat or combustion chamber15. At such point this eddy of air and fuel is ignited and llamestabilization is established.

The inner eddy creates a suction within the flame which tends to draweach particle of flame or remaining unconsurned air and fuel toward theaxis of the flame. The outer eddy serves for initial ignition withreduced air supply providing a rich mixture and then at normal air flow,

provides for re-ignition and stability. If the oil viscosity atatomizing temperature is too high, the heaviest particles are thrown outcentrifugally and are stagnated in this eddy forming a ring of cokewithin the throat. This may be corrected by raising the air temperatureor the oil tern* perature, with the air temperature predominatinginsecuring the proper low oil viscosity for eticient shearing oratomizing.

Within the tuyre it may be shown that the center line of force, inwardto the closed end 24 of the tuyre, de fines the boundary between thevortex existing as a vacuum and the rotating air mass existing underpressure. The outward dening line of force then creates an eddy withinthe tuyre adjacent the closed end which draws the fuel and air inwardlyand down.

The oil discharge from the nozzles is thus effected not only by thisinwardly moving fuel gas and eddy created by the outward spiralling rstline of force but also from the rapid rotational effect of the vortex. Astrong shearing action results. This is generally represented in Fig.

3 by the suggested path 35 of an oil droplet discharging l' from one ofthe nozzles 30. The oil is drawn violently into the eddy created by theoutwardly spiralling first line of force and is then swept against theburner end wall 24 and toward the center where the oil rings thevortexinterception 37 with the end wall. enough body to be acted on bycentrifugal force imparted by friction with the rotating air. The fuelis then thrown spirally outward and forward passing through laminarlayers of air, all whirling at different circumferential speeds. Thefuel is thus sheared as though it were fed r between two wheels ofdifferent rotation and homogenized therein.

It is of course to be understood that with a plurality of nozzles 3i)asV for example six equally spaced in a tuyre of seven inches diameter,there is such an overlapping of the fuel paths so that the discharge ofcombustible material appears uniform. I have found it essential that thenozzles 30 be spaced on a circle which comes between the walls of thevortical column X for I nd that with the high velocity of rotation thereis a substantial resistance by the inner wall of the column to theintroduction of a liquid fuel which causes an erratic distribution.There is a minimum of resistance in the area between the inner and outerwalls of the column.

I also tind that with the heavy fuels having a carbon content greaterthan distillate fuels, there is some tendency of segregation with theheavy portions designated Y thrown to the outer Wall. It will beapparent that the lightest oil is thus on the inner portion of theVortex and due to the heat radiation and flow of flue gases the lightoil is atomized quickest and in a path spiralling outward from thevortex circle. The residue being heavier, is subjected to a greatercentrifugal force and being further outward from the center axis issheared to a greater extent during its greater residence time and longerspiral Here it achieves path. As a result, it is estimated that theparticles `are broken down generally into `inicron size or less with faresulting very high temperature flame.

I have found that even with careful distribution of oil Within thevcolumn walls, and even with the desired high velocity of air, theasphalt feed sometimes tends to deposit droplets on the blades and kthuscause premature coking. It is apparent that the larger oil particles arethrown 'centrifugally outward thus striking the inner blade surfaces.There they are driven by the slant of the blades to the outer edge butat this point, due to the entering air, an eddy exists of quiet liquidand this rapidly cokes. The main air stream returns some of the dropletsthrough the blades but it plasters more against the back of the burnerface 20. This cannot be tolerated since it forms coke and partly closesthe holes 20a on which reliance isplaced for air cooling. It has alsobeen found that the velocity of the air enteringl the blades adjacentthe open end of the tuyre is consider-- ably less than the velocitythrough the blade adjacent theV closed end of the tuyre. I

With the heavy fuels, I have thus found it desirable to utilize a skirtor balile generally indicated 28 with a cylindrical portion uniformlysurrounding the major part of the tuyre and surmounted by the conicalportion 28a which connects the cylindrical portion with the outer partof the tuyre blades 22. A By virtue of the pressure drop thus imposed onthe air passing from the windbox through the skirt passage to theblades, a controlled velocity of air is established through the bladeswhich thus enters alongplanes which are substantially transverse to thetuyre axis. This not only assures reentrainment of any liquid whichmight become thrown out by the centrifugal force but also substantiallyprevents disentrainment by assuring the desired velocities along theblade length. J l

A good tuyre operation is secured with a proper balance between ythecentrifugal force on the atomized particles which throws them toward theblades andk there- `fore toward the blade entries (for fouling) onl theone hand and the centripetal component of the viscous drag of theincoming air on the other hand. In such case the particles can be `madeto rotate in a circular path in the burner so as to reduce bladeimpingement.

In sorne cases by proper dimensioning for suitable entering velocitiesto the blades, it may be possible to utilize the windbox 14 as the skirtbut generally it is easier to provide the particular desired skirt sizefor various burners rather than to change the windbox foreach differentoperating condition. Furthermore, I provide space for the air for theopenings 20a in the face plate which serves to cool the face plateduring operation. In other words, therear refractory 15a in thecombustion chamber is normally spaced about 1A', inch from the faceplate 20 and substantially overlapping it and .by passing approximately2-4% of the air through the openings 20a I and'under the projecting endof the refractory I can be assured of a long-lived face plate. Therefractory shield is generally satisfactory although I have also used aspaced alloy shield as described in my copending application Serial No.98,976, now Patent Number 2,560,076.

kThe alloy shield is unsatisfactory in the presence of vanadiumcontaining fuels because of catalyticoxidation. The use of the shieldand the cooling airhas reduced the temperature of the face plate from1300,-1400 F. to a temperature in the range of 700 F. I have alsodescribehd in my said Patent No. 2,560,076, a form of skirt `whichsurrounds an intermediate part of the tuyre and may be made of suchdiameter and position that differential velocities of air through therespective portions of the blades are obtained. With a burner where themajor problem is t'o prevent dis-entrainment and to assurere-entrainment, the skirt must be substantially coextensive with thetuyre. It will be apparent that a great many varieties may be used butfor practical purposes,

lI ha-vefound'the structures zofFigs; land 4 to be most ,effective andleast lcomplicated.

In Fig. 4, the tuyre 18 having'thetypicalfront face 20, :is v:providedwitha imultiplediameter .skirt-'38 hav- :ing .a rst conical section 39,,a cylindrical portion 40 .and a closingcone 4i. This .type whichdiminishes in .diametervin-an outward direction tends `more effectivelythan-that shown in Fig. -l .to increase the velocity through the-.bladesnearest .the open end of thev tuyre, and thereiluy-.preventsdisentrainment of Yfuel from the air column.

Other constructions have been tried with more or less ,success includinga `right cone, axcylinder, and -an in- ',verted multiple rdiameter skirtof the type shown in `Fig. 4 but sealed with respect to the closed endwall of the Atuyre. v

,-I have also used directional vanes 43 as shown in Fig. ,3 Aby whichthe entering air wwhich `normally passes .axially with respect lto thetuyre as it moves through `the windbox is given an angular componentYtending to .give a more nearly tangential inlet V,between the blades.

lt will also be apparent that streamlining-of the blades -and otherparts can .be utilized in the interest-of saving .pressure drop. Thestructureas shown in Fig. l however ,is commercially satisfactoryalthough the detailed improvements will be used if their economy ofoperation exceeds the cost of making the changes.

The use of preheated air with residual fuels is quite important fromkthe standpoint of coke free operation. Where fine atomization in theorder of 100 microns or .less isdesired, the fuel must be in conditionfor intimate Vdispersion in the air.

It has been my experience ,that a yviscosity range'of 20 to 50centistokes is most eiective `and with residual fuel oils thetemperature of the air should be from ZOO-250 F. 'With asphalticresidues, the temperature of the air of from 350-450 F. will giveapproximately the same results. The preheated lair, of course, increasesthe eiiciency of the burner.

Atypical installation of this type had substantially the followingdimensions:

The range of burner sizes for various duties is generally found in thefollowing table, it being understood that by varying the air velocity, arangeof operation of from 70 to 140% may be obtained in any burner.

Cepam MMX MMI M11 MMl Mnl Tuyre Diameter 3 l 7% 10 B. 7 'Tuyre Length 36 9 9 l2 Curb or Chamber Diameter" l0 t 20 22% 28 30 Curb or ChamberLength 1S i 2O t V2?' 27 30 `rFusie.. Gals. per hone-Bunker G".. 7/2 32l 48 72 S0 MM is equal 1.o 1,000,000 British thermal units.

A closed name pattern canbe obtained within the combustion chamber if ithas the critical dimensions characteristic of the chamber in Fig. l. Thechamber should notbe less in-diameter than about 11/2 Atimes thediameter o'f the tuyre opening and it should be not greater than 4times, and preferably 3 times the diameter of the tuyre opening. inlength, the combustion chamber shouldbe nearlyas long Vas its diameter.

'I have lnot 'found vit necessary Ito use secondary air for combustionpurposes. :Howeverrmany furnace operators choose to introduce secondaryair for various reasons. Thismay be introduced .at anydesired pointforany of the ,desired freasons such as rcooling bridge walls, etc. Theburner'is .normally designed forno excess air operation at'rfwater gaugeand operates at a maximum-of 20 -percent excess at nine inches, normalrating. The

burner has an operating range of 70% capacityto 125% capacity. For lowervelocities of air, the llame pattern becomes ragged and uneven withpossible formations of coke with heavy fuel feed.

An important feature of the direct combustion of asphalt will beapparent from a typical disposal problem. In the particular case, it wasdesired to disposeof Y200 barrels per day of asphalt from a propaneextraction process. This was blended with an equal amountofdisavailability of fuel, the voperator may choose to run gas,

distillate, reduced crudes, or even the asphaltic residues. The burnercan burn simultaneously two or more mixtures, the arne continuing to .beshort, brilliant, smoke free and ash free. The increased flametemperature makes possible higher-heat input rates andfurther reducescosts of alliedequipment. The burner is shown in horizontal position inFig, l butit-has also been shown in vertical position in the companioncopending cases, Serial No. 66,445 andSerial No. 98,976, now Patents No.2,560,- 074'and 2,560,076. It will work equally well in angularpositions due to the fact that the velocity of air is so great that theestablished gravitational .effect of the vortex is little influenced bygravity.

A port 50 is provided thru therback refractory surface surrounding theburner face. A lighted gas torch lwith no air premix is inserted in theport and completes its combustion on the back of the Vwhirling airpattern in the refractory throat, remaining permanently lit. When l fuelgas is admitted tothe burner, combustion is immediate.stoichiometric-rthecombustionis colorless and transparent and evidentonly from the radiant refractory throat.

Recommendedl practice is to then cut over to fuel oil to 'ush and warmYthe feed lines and valving. It was possible with a vigorous pilot flameto omit the intermediate step of gas firing, `igniting the highlyatomized fuel oil even in a cold refractory throat, though best practiceis to provide for initial` gas firing.

VAsphalt then follows thefuel oil and burns Vwith an even more dazzlingwhite incandescent flame because of its increased viscosity andhighercarbon residue.

Prior to a shutdown fuel oil is again resorted tofor flushing the burnerand lines. In cold climates the burner lines may be purged by the gas.

Where it is forbidden to light aftorch outside `the furnace thegas-electric method of'ignition may be used for starting or continuingthe vpilot light.

While-I have shown and describeda preferred .forrn of burner inaccordance with my invention, .I ,am aware that modifications maybe-made thereto which are within theY scope and spirit of my invention.

I claim: Y Y

1. In a liquid fuel burner, an open ended vhollow annular tuyre having aclosed end wall, and a side wall having a plurality of kfixedsubstantially tangential blades extending .throughout the major part ofsaid side wall and forming inwardly convergent airpaths, an enclosuresurrounding said tuyre,.rneanszforsupplying .an air cur` rent to saidenclosure fand through said air paths between said blades to establish avortical air column in lsaid The saving in directy Because the fuelgas-air ratio is substantiallyy tuyre, fuel supply means adjacent theclosed end wall of said tuyre adapted to communicate with the vorticalair column whereby said fuel is entrained in said column and dischargedthrough the open end of the tuyre, said fuel supply means including aplurality of nozzles extending through the closed end wall of the tuyrein spaced relation to the side wall and at such a radial distance fromthe center that the vortical air column therein normally covers thedischarge openings, and a fuel distributing pan surrounding the closedend wall of the tuyre, the wall of said pan forming with the edge of theblades a plurality of peripherally spaced fuel passages, and separateconduit means to supply fuel to said nozzles and pan.

2. In a liquid fuel burner, an open ended hollow cylindrical tuyrehaving a closed end wall, and a side wall having a plurality of fixedsubstantially tangential blades extending throughout the major partthereof and forming inwardly convergent air inlet paths, an enclosuresurrounding said tuyre, means for supplying air to said enclosure andthrough said air paths between said blades for forming a hollow,swirling, forwardly moving vortex of air in said tuyre adjacent the sidewall, a plurality of fuel feeding nozzles extending a short distancethrough the closed end wall of the tuyre in spaced relation to the sidewall and at such a radial distance from the center that the portion ofthe forwardly moving vortex of air adjacent the closed end wall in thetuyre normally covers the nozzle openings, and an annular skirt Withinthe enclosure surrounding the tuyre and sealed with respect to the openend thereof, the other end of the skirt being spaced from the tuyre toreceive the air entering the enclosure and direct it through the tuyreinlet paths, the cross sectional area of the skirt portion adjacent theopen end of the tuyre being less than that at the closed end of thetuyre whereby the velocity of the air entering the tuyre is increasednear the open end to restrain fuel disentrainment.

3. In a liquid fuel burner as claimed in claim 2 in vwhich said annularskirt has multiple cylindrical sections of different diameter which arejoined by conical sections to each other and to the open end of thetuyre.

4. In a liquid fuel burner, an open ended hollow cylindrical tuyrehaving a closed end wall and a side Wall having a plurality of fixedsubstantially tangential air inlet slots extending throughout the majorpart thereof and forming inwardly directed air inlet paths, an enclosuresurrounding said tuyre means for supplying air to said enclosure andthrough said air inlet paths for forming a hollow, swirling, forwardlymoving vortical column of air in said tuyre adjacent the side wallthereof, annular baflle means within the enclosure extending the lengthof the air inlet slots and in the path of the supplied air to maintain avelocity of air through the air inlet paths at all parts of the vorticalcolumn at least equal to the velocity adjacent the closed end of thetuyre to prevent disentrainment of fuel from the air column, liquid fue]feeding means including a plurality of nozzle openings disposed withinthe interior of the tuyre a short distance from the closed end wall andat such a radial distance from the center that the portion of theforwardly moving vortical column of air adjacent said closed end wall inthe tuyre normally covers the nozzle openings, and means to supplyliquid fuel to said nozzle openings whereby fuel is entrained in saidvortical column of air.

References Cited in the file of this patent UNITED STATES PATENTS1,795,454 Van Brunt Mar. 10, 1931 2,458,992 Hague Ian. 11, 19492,560,076 Bloomer July 10, 1951 FOREIGN PATENTS 350,051 Great BritainJune 11, 1931

1. IN A LIQUID FUEL BURNER, AN OPEN ENDED HOLLOW ANNULAR TUYERE HAVING A CLOSED END WALL, AND A SIDE WALL HAVING A PLURALITY OF FIXED SUBSTANTIALLY TANGENTIAL BLADES EXTENDING THROUGHOUT THE MAJOR PART OF SAID SIDE WALL AND FROMING INWARDLY CONVERGENT AIR PATHS, AN ENCLOSURE SURROUNDING SAID TUYERE, MEANS FOR SUPPLYING AN AIR CURRENT TO SAID ENCLOSURE AND THROUGH SAID AIR PATHS BETWEEN SAID BLADES TO ESTABLISH A VORTICAL AIR COLUMN IN SAID TUYER, FUEL SUPPLY MEANS ADJACENT THE CLOSED END WALL OF SAID TUYERE ADAPTED TO COMMUNICATE WITH THE VERTICAL AIR COLUMN WHEREBY SAID FUEL IS ENTRAINED IN SAID COLUMN SAID DISCHARGED THROUGH THE OPEN END OF THE TUYERE, SAID FUEL SUPPLY MEANS INCLUDING A PLURALITY OF NOZZLES EXTENDING THROUGH THE CLOSED END WALL OF THE TUYERE IN SPACED RELATION TO THE SIDE WALL AND AT SUCH A RADIAL DISTANCE FROM THE CENTER THAT THE VERTICAL AIR COLUMN THEREIN NORMALLY COVERS THE DISCHARGE OPENINGS, AND A FUEL DISTRIBUTING PAN SURROUNDING THE COLSED END WALL OF THE TUYERE, THE WALL OF SAID PAN FORMING WITH THE EDGE OF THE BLADES A PLURALITY OF PERIPHERALLY SPACED FUEL PASSAGES, AND SEPARATE CONDUIT MEANS TO SUPPLY FUEL TO SAID NOZZLES AND PAN. 